4-Aryl-bis 2,6-(aminophenyl)pyridines

ABSTRACT

Novel 4-aryl-or heteroaryl-2,6-bis[(substituted-amino)phenyl]pyridines which are useful as color formers in pressure-sensitive carbonless duplicating systems and thermal marking systems are prepared by reacting a 2-, 3- or 4-R1R2N-acetophenone with an aryl or heteroaryl aldehyde in the present of ammonia or an ammonia-releasing agent.

This application is a division of application Ser. No. 243,798 filedMar. 16, 1981 now U.S. Pat. No. 4,363,505.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a group of compounds classified in the fieldof organic chemistry as 4-aryl orheteroaryl-2,6-bis[(substituted-amino)phenyl]pyridines useful as colorformers in pressure-sensitive carbonless duplicating systems and thermalmarking sytems, to a process for the preparation thereof and topressure-sensitive carbonless duplicating systems and thermal markingsystems containing the same.

2. Description of the Prior Art

Several classes of organic compounds of widely diverse structural typesare known to be useful as color formers for carbonless duplicatingsystems. Among the more important classes are the phenothiazines, forexample N-benzoyl leuco methylene blue; fluorans, for example2'-anilino-6'-diethylaminofluoran; phthalides, for example crystalviolet lactone; arylsulfinate salts of Michler's Hydrol; substitutedphenylpyridines and various other types of colorless precursorscurrently employed in commercially accepted carbonless copy systems.Typical of the many such systems taught in the prior art are thosedescribed in U.S. Pat. Nos. 2,712,507, 2,800,457, 3,041,289 and4,000,087, which issued July 5, 1955, July 23, 1957, June 26, 1962 andDec. 28, 1976, respectively. Many of the color formers in the prior artsuffer one or more disadvantages such as low tinctorial strength, poorlight stability, poor xerographic copiability and low solubility incommon organic solvents, the latter disadvantage thus requiring the useof specialized and expensive solvents in order to obtainmicroencapsulated solutions of sufficient concentration for use inpressure-sensitive copy systems.

The following appear to constitute the most pertinent prior art relativeto the present invention.

Baumann et al., U.S. Pat. No. 3,985,376, patented Oct. 12, 1976 disclosecompounds of the formula: ##STR1## in which

R¹ and R² are hydrogen or alkyl or aryl of one to eight carbon atomswhich may bear alkoxy or halogen as a substituent;

R³ is hydrogen or alkyl of one to five carbon atoms;

R⁴ is alkyl, haloalkyl, cyanalkyl, aryl or aralkyl of one to eightcarbon atoms which may bear alkoxy as a substituent;

R⁵ and R⁶ are hydrogen or carbalkoxy of two to five carbon atoms and R³and R⁴ may be closed to form a ring. Specific compounds disclosed arethose wherein R¹ and R² are each phenyl, R⁵ and R⁶ are each hydrogen, R³is methyl and R⁴ is methyl, phenyl or p-ethoxyphenyl, and also thosewherein R¹ and R² are each p-methoxyphenyl, R⁵ and R⁶ are each hydrogenand R³ and R⁴ are each methyl. The compounds are stated to be useful asdye precursors for pressure-sensitive recording material.

Frank and Seven, J. Amer. Chem. Soc. 71, 2629-2635 (1949) disclose4-(p-chlorophenyl)-2,6-diphenylpyridine, 4-anisyl-2,6-diphenylpyridineand 2,6-diphenyl-4-(m-methoxyphenyl)pyridine. These compounds wereisolated as reaction products in a study of the Chichibabin reaction.

M. Weiss, J. Amer. Chem. Soc. 74, 200-202 (1952) discloses in mostpertinent part compounds of the formula ##STR2## wherein R is hydrogen,and R' is phenyl, 4-methoxyphenyl, 3,4-methylenedioxyphenyl,4-dimethylaminophenyl or 2-methoxyphenyl. These compounds were isolatedas reaction products in a study of the Chichibabin synthesis.

E. Koenigs and E. Ruppelt, Ann. 509, 142-158 (1934) disclose as basicdyestuffs a number of 4-[p-dialkylaminophenyl]pyridines.

Gilman et al., J. Org. Chem. 22, 1169-1171 (1957) in most pertinent partdisclose 2,6-bis(p-diethylaminophenyl)pyridine as a relatively weakliquid scintillator solute.

3. Prior Publications

The following United Kingdom Patent application was published prior tothe filling of applicants' instant application but subsequent to thecomposition of applicants' invention.

United Kingdom Patent application No. 2,029,591A, published Mar. 19,1980 discloses pyridine derivatives having the formula ##STR3## wherein

R₁ and R₂ are independently hydrogen, phenyl group orchlorine-substituted phenyl groups;

R₃ is hydrogen, lower-alkyl groups or lower-alkoxy groups;

R₄ and R₅ are independently lower-alkyl groups, benzyl group or phenylgroup, said lower-alkyl groups possibly being substituted with a cyanogroup, a chlorine atom or a lower-alkoxy group. The compounds are statedto produce a yellow color on heating in the presence of an electronacceptor.

SUMMARY OF THE INVENTION

The present invention provides novel 4-aryl- orheteroaryl-2,6-bis[(substituted-amino)phenyl]pyridines useful as colorformers in pressure-sensitive carbonless duplicating systems and thermalmarking systems. The compounds develop light-stable colored images ofgood tinctorial strength, and are soluble in common organic solvents.Moreover, because the compounds produce yellow to orange colors, theyare especially valuable as toners used in admixture with other colorformers to produce images of a neutral shade. The invention alsoprovides a process for the preparation of these compounds as well aspressure-sensitive carbonless duplicating systems and thermal markingsystems containing them.

In a composition of matter aspect the invention relates to a series of4-aryl- or heteroaryl-2,6-bis(2-,3- or 4-R₁ R₂ N-phenyl)pyridines whichare useful as color formers in pressure-sensitive carbonless duplicatingsystems and thermal marking systems.

In a process aspect, the present invention provides a process forpreparing 4-aryl- or heteroaryl-2,6-bis(2-,3- or 4-R₁ R₂N-phenyl)pyridines which comprises reacting a 2-,3- or 4-R₁ R₂N-acetophenone with an aryl or heteroaryl aldehyde in the presence ofammonia or an ammonia-releasing agent.

In an article of manufacture aspect the present invention relates to apressure-sensitive carbonless duplicating system or thermal markingsystem containing a color-forming substance comprising at least one ofthe 4-aryl- or heteroaryl-2,6-bis[(substituted-amino)phenyl]pyridines ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION INCLUSIVE OF THE PREFERREDEMBODIMENTS

In a composition of matter aspect the invention sought to be patentedresides in a compound having Formula I hereinbelow: ##STR4## wherein:

R₁ and R₂ are the same or different and are selected from the groupconsisting of lower-alkyl and benzyl, or

NR₁ R₂ is pyrrolidinyl, piperidinyl or morpholinyl;

Z is naphthyl, 9-julolidinyl or a substituent having the formula:##STR5## wherein

R₃, R₄, R₇ and R₈ are hydrogen or non-tertiary lower-alkyl;

R₅ is hydrogen, phenyl or non-tertiary lower-alkyl;

R₆ is hyrogen, non-tertiary lower-alkyl or non-tertiary lower-alkoxy;

X is O or S;

Y₁ and Y₂ are the same or different and are selected from the groupconsisting of hydrogen, lower-alkyl, lower-alkoxy, halo, nitro,lower-alkoxycarbonyl, phenyl or NR₉ R₁₀ ;

R₉ is lower-alkyl or benzyl;

R₁₀ is lower-alkyl, benzyl, cyano-lower-alkyl, or

NR₉ R₁₀ is pyrrolidinyl, piperidinyl, morpholinyl or isoindolinyl.

These compounds are useful as color formers for pressure-sensitivecarbonless duplicating systems and thermal marking systems.

A particular embodiment sought to be patented resides in a compoundhaving Formula I hereinabove wherein R₁ and R₂ have the previously givenmeanings and Z is a substituent having the formula ##STR6## Preferredcompounds within the ambit of this embodiment are those wherein Y₁ andY₂ are the same or different and are selected from the group consistingof hydrogen, lower-alkyl and lower-alkoxy and where R₁ and R₂ are eachlower-alkyl, especially2,6-bis[4-(dimethylamino)phenyl]-4-phenylpyridine,2,6-bis[4-(dimethyl)phenyl]-4-(4-methylphenyl)pyridine and2,6-bis[4-(dimethylamino)phenyl]-4-(4-methoxyphenyl)pyridine. Alsopreferred are the compounds wherein R₁ and R₂ are each lower-alkyl andone of Y₁ and Y₂ is NR₉ R₁₀, R₉ and R₁₀ each being lower-alkyl,especially 2,4,6-tris[4-(dimethylamino)phenyl]pyridine. These compoundsare particularly valuable because they are easily prepared frominexpensive and readily available starting materials.

In its process aspect, the invention sought to be patented resides in aprocess for preparing the compounds of Formula I hereinabove whichcomprises reacting approximately 2 molar equivalents of an acetophenonehaving Formula II hereinbelow: ##STR7## with approximately 1 molarequivalent of an aryl or heteroaryl aldehyde having Formula IIIhereinbelow:

    Z--CHO Formula III

in the presence of ammonia or an ammonia-releasing agent where inFormulas II and III, R₁, R₂ and Z have the previously given meanings.

In an article of manufacture aspect the invention sought to be patentedresides in a pressure-sensitive carbonless duplicating system or thermalmarking system containing a support sheet coated with a color-formingsubstance comprising a compound having Formula I hereinabove.

A particular embodiment sought to be patented resides in apressure-sensitive transfer sheet adapted for use with a receiving sheethaving an electron-accepting layer comprising a support sheet coated onone side with a layer of pressure-rupturable microcapsules, saidmicrocapsules containing a liquid solution of a color-forming substancecomprising at least one compound having Formula I.

Another particular embodiment sought to be patented resides in aheat-responsive record material comprising a support sheet coated on oneside with a layer containing a mixture comprising at least onecolor-forming compound having Formula I and an acidic developer arrangedsuch that application of heat will produce a mark-forming reactionbetween the color-forming compound and the acidic developer.

A further embodiment sought to be patented resides in apressure-sensitive carbonless duplicating system or a thermal markingsystem containing a support sheet coated with a color-forming substancecomprising a compound having Formula I hereinabove in combination with ablue or green and a red or orange color former.

Preferred articles within the ambit of the particular embodimentsabove-described as those having a color-forming component of Formula Ihereinabove in which R₁ and R₂ have the previously given meanings and Zis a substituent having the formula ##STR8## especially where Y₁ and Y₂are the same or different and are selected from the group consisting ofhydrogen, lower-alkyl and lower-alkoxy or where one of Y₁ and Y₂ isdi-lower-alkylamino and where R₁ and R₂ are each lower-alkyl.

As used herein the term "halo" includes fluoro, chloro, bromo and iodo.

In the terms "lower-alkyl", "cyano-lower-alkyl", "lower-alkoxy" and"lower-alkoxycarbonyl", "lower-" denotes a saturated acyclic alkylmoiety having from 1 to 4 carbon atoms such as methyl, ethyl, propyl,isopropyl, butyl, sec-butyl or isobutyl.

The term "9-julolidinyl", of course, refers to the radical having theformula ##STR9##

In accordance with the process aspect of this invention the compoundshaving Formula I hereinabove are obtained by reacting approximately twomolar equivalents of an acetophenone of Formula II hereinabove withapproximately one molar equivalent of an aryl or heteroaryl aldehyde ofFormula III hereinabove in the presence of ammonia or anammonia-releasing agent. Thus, the acetophenone and aldehyde can becondensed in the presence of aqueous or alcoholic ammonia oralternatively, and preferably, in the presence of an ammonia-releasingagent such as ammonium acetate in acetic acid. The reactants are heatedat about 50°-150° C. for approximately 1 to 5 hours, usually at thereflux temperature of the solvent for about 2 hours. The product thusobtained can be isolated by filtration if it is insoluble in thereaction medium, or by dilution of the reaction medium with a misciblesolvent in which the product is insoluble such as water or alower-alkanol, for example, isopropyl alcohol, or a mixture of these inorder to effect precipitation of the product. Alternatively, thereaction mixture can be poured into water or dilute ammonium hydroxideand the product extracted with an organic solvent such as benzenetoluene or chloroform followed by evaporation of the organic solventleaving the product as a residue. Frequently the product begins toseparate from the reaction mixture as an oil. Usually the addition of alower-alkanol such as ethanol or isopropyl alcohol to the hot reactionwill induce the product to separate in crystalline form on cooling. Theproduct once isolated can be purified by conventional means such astrituration or recrystallization from a suitable solvent.

The acetophenones of Formula II and the aldehydes of Formula III whichare required as starting materials in the preparation of the finalproducts of Formula I are generally known and are either commerciallyavailable or readily obtained by conventional procedures well known inthe art. Those acetophenones and aldehydes which are specifically novelcan be prepared in accordance with the procedures described forpreparation of the known compounds.

The novel compounds of Formula I hereinabove are pale yellow tocolorless in the depicted form. When contacted with an acidic medium,for example silica gel, or one of the types ordinarily employed inpressure-sensitive carbonless duplicating systems such as silton clay orphenolic resins, the compounds of Formula I develop an intense yellow toorange image which is xerographically copiable and light stable. Thecompounds are thus highly suitable for use as color precursors, that is,color-forming substances in pressure-sensitive carbonless duplicatingsystems. Because they produce a yellow to orange color, these compoundsare especially valuable as toners which are used in admixture with othercolor formers to produce images of a neutral shade which desirablypossess excellent xerographic copiability. Thus, a yellow to orangecolor former of Formula I hereinabove can be combined with a red ororange color former and a blue or green color former to afford acolor-forming substance which produces a neutral or black image.

The compounds of this invention may be incorporated in any of thecommercially accepted systems known in the carbonless duplicating art. Atypical technique for such application is as follows: solutionscontaining one or more color precursor compounds of Formula I,optionally in admixture with other color formers as noted above, insuitable solvents are microencapsulated by well-known procedures, forexample as described in U.S. Pat. Nos. 3,649,649, 3,429,827 and4,000,087. The microcapsules are coated on the reverse side of atransfer sheet with the aid of a suitable binder and the coated transfersheet is then assembled in a manifold with the microcapsule-coated sidein contact with a receiving sheet coated with an electron acceptingsubstance for example silton clay or phenolic resin. Application ofpressure to the manifold such as that exerted by a stylus, typewriter orother form of writing or printing causes the capsules on the reverseside to rupture. The solution of the color former released from theruptured microcapsules flows to the receiving sheet and on contact withthe acidic medium thereon forms a colored image. It is, of course,obvious that variants of this mode of application can be utilized. Forexample, the receiving sheet in a manifold can alternatively be coatedwith the subject compounds and the acidic developing agent can becontained in microcapsules applied on the reverse side of the top sheetin the manifold; or the receiving sheet can be coated with a mixturecontaining both the acidic developing agent and the microencapsulatedcolor former.

It has also been found that when the compounds of Formula I areintimately mixed with an acidic developer of the type generally employedin thermal papers such as described in U.S. Pat. Nos. 3,539,375 and3,447,944, that is, papers which produce a colored image when contactedwith a heated stylus or heated type, for example, bisphenol A, heatingof the mixture produces a colored image of varying shades from yellow toorange depending on the particular compound of the invention employed.As noted above, darker shades can be produced by mixing the compounds ofFormula I with other color formers. The ability of the compounds ofFormula I to form an intense color when heated in admixture with anacidic developer such as bisphenol A makes them useful in thermal papermarking systems either where an original or duplicate copy is preparedby contacting the thermal paper with a heated stylus or heated type inany of the methods generally known in the art.

The molecular structure of the compounds of this invention were assignedon the basis of the modes of synthesis, elemental analysis and study oftheir infrared and nuclear magnetic resonance spectra.

The following examples will further illustrate the invention withouthowever limiting it thereto.

EXAMPLE 1

A mixture containing 4.2 g. of 4-anisaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 36 g. of ammonium acetate and 50 ml. ofglacial acetic acid was refluxed for one hour and was then allowed tostand at room temperature overnight. The mixture was filtered and thecollected solid was washed with isopropanol and water. The solid wasthen slurried in 100 ml. of hot isopropanol. After cooling to roomtemperature, the pale yellow solid was collected, washed withisopropanol and dried to give 3.9 g. of4-(4-methoxyphenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, m.p.194°-197° C. This product produced an orange image on contact withacidic clay or phenolic resin.

EXAMPLE 2

A mixture containing 3.2 g. of benzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 30 g. of ammonium acetate and 75 ml. ofglacial acetic acid was refluxed for two hours. After cooling to roomtemperature, the reaction mixture was poured into 300 ml. of toluene and400 ml. of 5% aqueous ammonium hydroxide. The toluene layer wasseparated, washed successively with ater and saturated aqueous sodiumchloride and evaporated to dryness under vacuum. The residue wasslurried in ethanol and collected by filtration to give 2.1 g. of4-phenyl-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a pale yellowsolid, m.p. 176°-179° C. A toluene solution of the product developed anorange image when contacted with acidic clay and a yellow image whencontacted with phenolic resin.

EXAMPLE 3

Following a procedure similar to that described in Example 1 butemploying 4.0 g. of 4-methylbenzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 35 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 3.8 g. of4-(4-methylphenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a palegreenish yellow solid, m.p. 210°-222° C. This product produced an orangeimage on contact with acidic clay or phenolic resin.

EXAMPLE 4

Following a procedure similar to that described in Example 2 butemploying 4.5 g. of 4-(dimethylamino)benzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 30 g. of ammonium acetate and 75 ml. ofglacial acetic acid there was obtained 2.3 g. of2,4,6-tris[4-(dimethylamino)phenyl]pyridine, as a yellow solid, m.p.256°-260° C. This product produced a yellow image on contact with acidicclay or phenolic resin.

EXAMPLE 5

Following a procedure similar to that described in Example 2 butemploying 4.2 g. of 4-chlorobenzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 36 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 2.4 g. of4-(4-chlorophenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a paleyellow solid, m.p. 178°-182° C. This product produced a yellowish-orangeimage on contact with acidic clay or phenolic resin.

EXAMPLE 6

Following a procedure similar to that described in Example 2 butemploying 5.5 g. of 2-chloro-4-(dimethylamino)benzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 35 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 3.4 g. of4-[2-chloro-4-(dimethylamino)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a pale yellow solid, m.p. 131°-139° C. The product produced a yellowimage on contact with acidic clay or phenolic resin.

EXAMPLE 7

Following a procedure similar to that described in Example 1 butemploying 4.5 g. of 4-nitrobenzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 35 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 5.5 g. of4-(4-nitrophenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a yellowsolid, m.p. 156°-164° C. This product produced an orange image oncontact with acidic clay or phenolic resin.

EXAMPLE 8

Following a procedure similar to that described in Example 2 butemploying 5.6 g. of 4-[(2-cyanoethyl)methylamino]benzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 35 ml. ofglacial acetic acid there was obtained 3.5 g. of4-[4-[(2-cyanoethyl)methylamino]phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a light yellow solid, m.p. 170°-174° C. This product produced anorange-yellow image on contact with acidic clay or phenolic resin.

EXAMPLE 9

Following a procedure similar to that described in Example 2 butemploying 5.0 g. of 2,5-dimethoxybenzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid, there was obtained 2.5 g. of4-(2,5-dimethoxyphenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as alight yellow solid, m.p. 199°-206° C. This product produced a yellowishorange image on contact with acidic clay or phenolic resin.

EXAMPLE 10

A mixture containing 4.5 g. of 3-nitrobenzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 40 ml. ofglacial acetic acid was refluxed for two hours. After cooling to roomtemperature, the resulting tarry solid was collected and was firstslurried in isopropanol then in toluene to give 3.0 g. of4-(3-nitrophenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a yellowsolid, m.p. 194°-200° C. This product produced a yellowish-orange imageon contact with acidic clay or phenolic resin.

EXAMPLE 11

A mixture containing 4.6 g. of methyl 4-formylbenzoate, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid was heated 3 hours under reflux. The mixture wascooled to 70° C. and 75 ml. of isopropanol was added, reheated to90°-95° C. and held for 30 minutes. After cooling to room temperature,the yellow solid was collected, washed with isopropanol and dried togive 3.9 g. of4-[4-(methoxycarbonyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,m.p. 244°-250° C. This product produced an orange image on contact withacidic clay or phenolic resin.

EXAMPLE 12

Following a procedure similar to that described in Example 2 butemploying 5.4 g. of 4-(diethylamino)benzaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 30 g. of ammonium acetate and 75 ml. ofglacial acetic acid there was obtained 1.0 g. of4-[4-(diethylamino)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine as ayellow solid, m.p. 193.9°-201.8° C. A toluene solution of the productdeveloped an orange image when contacted with acidic clay and a yellowimage when contacted with phenolic resin.

EXAMPLE 13

Following a procedure similar to that described in Example 1 butemploying 4.0 g. of 4-biphenylcarboxaldehyde, 6.5 g. of4-(dimethylamino)acetophenone, 27 g. of ammonium acetate and 25 ml. ofglacial acetic acid there was obtained 3.0 g. of4-(4-biphenylyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a yellowsolid, m.p. 213°-216° C. This product produced an orange image oncontact with acidic clay or phenolic resin.

EXAMPLE 14

Following a procedure similar to that described in Example 1 butemploying 4.7 g. of 1-naphthaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 35 ml. ofglacial acetic acid there was obtained 3.6 g. of4-(1-naphthyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a lightyellow solid, m.p. 189°-208° C. A chloroform solution of the productdeveloped an orange image when contacted with acidic clay and a yellowimage when contacted with phenolic resin.

EXAMPLE 15

Following a procedure similar to that described in Example 2 butemploying 6.0 g. of 4-(1-pyrrolidinyl)benzaldehyde, 11 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 4.7 g. of4-[4-(1-pyrrolidinyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a yellow solid, m.p. 199.8°-214.9° C. This product produced a yellowimage on contact with acidic clay or phenolic resin.

EXAMPLE 16

Following a procedure similar to that described in Example 1 butemploying 6.3 g. of 4-(1-piperidinyl)benzaldehyde, 11 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 5.2 g. of4-[4-(1-piperidinyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine asa yellow solid, m.p. 217.5°-220.9° C. A chloroform solution of theproduct developed an orange image when contacted with acidic clay and ayellow image when contacted with phenolic resin.

EXAMPLE 17

Following a procedure similar to that described in Example 1 butemploying 5.6 g. of 4-(2-isoindolinyl)benzaldehyde, 8.5 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 4.0 g. of4-[4-(2-isoindolinyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine asa muddy yellow solid, m.p. 265°-271° C. A chloroform solution of theproduct developed an orange image when contacted with acidic clay and ayellow image when contacted with phenolic resin.

EXAMPLE 18

Following a procedure similar to that described in Example 11 butemploying 3.0 g. of 4-(4-morpholinyl)benzaldehyde, 5.0 g. of4-(dimethylamino)acetophenone, 25 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 2.2 g. of4-[4-(4-morpholinyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine asa pale yellow solid, m.p. 231°-234° C. A chloroform solution of theproduct developed an orange image when contacted with acidic clay and ayellow image when contacted with phenolic resin.

EXAMPLE 19

Following a procedure similar to that described in Example 2 butemploying 4.8 g. of 2-methyl-4-(1-pyrrolidinyl)benzaldehyde, 8.5 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 50 ml. ofglacial acetic acid there was obtained 2.6 g. of4-[2-methyl-4-(1-pyrrolidinyl)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a yellow solid, m.p. 225°-229° C. A chloroform solution of theproduct developed an orange image when contacted with acidic clay and ayellow image when contacted with phenolic resin.

EXAMPLE 20

Following a procedure similar to that described in Example 2 butemploying 5.1 g. of 9-julolidinecarboxaldehyde, 8.2 g. of4-(dimethylamino)acetophenone, 33 g. of ammonium acetate and 25 ml. ofglacial acetic acid there was obtained 3.5 g. of4-(9-julolidinyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as anorange-yellow solid, m.p. 237°-249° C. This product produced ayellowish-orange image on contact with acidic clay or phenolic resin.

EXAMPLE 21

Following a procedure similar to that described in Example 11 butemploying 5.1 g. of 4-anisaldehyde, 9.8 g. of3-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 35 ml. ofglacial acetic acid there was obtained 2.5 g. of4-(4-methoxyphenyl)-2,6-bis[3-(dimethylamino)phenyl]pyridine, as a milkywhite solid, m.p. 187°-189° C. This product produced a weak yellow imageon contact with acidic clay or phenolic resin.

EXAMPLE 22

Following a procedure similar to that described in Example 2 butemploying 3.2 g. of benzaldehyde, 9.8 g. of3-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 35 ml. ofglacial acetic acid there was obtained 2.0 g. of4-phenyl-2,6-bis[3-(dimethylamino)phenyl]pyridine, as an off-whitesolid, m.p. 142°-147° C. This product produced a weak orange image oncontact with acidic clay or phenolic resin.

EXAMPLE 23

Following a procedure similar to that described in Example 2 butemploying 3.6 g. of 4-methylbenzaldehyde, 11.5 g. of4-(diethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 2.0 g. of4-(4-methylphenyl)-2,6-bis[4-(diethylamino)phenyl]pyridine, as a yellowsolid, m.p. 174°-178.5° C. This product produced an orange image oncontact with acidic clay or phenolic resin.

EXAMPLE 24

Following a procedure similar to that described in Example 2 butemploying 4.1 g. of 4-anisaldehyde, 11.5 g. of4-(diethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 2.0 g. of4-(4-methoxyphenyl)-2,6-bis[4-(diethylamino)phenyl]pyridine as abrownish-yellow solid, m.p. 77°-87.5° C. This product produced ayellowish-orange image on contact with acidic clay or phenolic resin.

EXAMPLE 25

Following a procedure similar to that described in Example 11 butemploying 4.1 g. of 4-anisaldehyde, 21 g. of4-(dibenzylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 5.5 g. of4-(4-methoxyphenyl)-2,6-bis[4-(dibenzylamino)phenyl]pyridine as a yellowsolid, m.p. 72.3°-77.5° C. This product produced a yellow image oncontact with acidic clay or phenolic resin.

EXAMPLE 26

Following a procedure similar to that described in Example 2 butemploying 3.4 g. of 4-anisaldehyde, 10.2 g. of4-(1-piperidinyl)acetophenone, 35 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 3.4 g. of4-(4-methoxyphenyl)-2,6-bis[4-(1-piperidinyl)phenyl]pyridine, as anoff-white solid, m.p. 114°-118° C. This product produced a yellow imageon contact with acidic clay or phenolic resin.

EXAMPLE 27

A mixture containing 4.6 g. of 4-anisaldehyde, 14 g. of4-(4-morpholinyl)acetophenone, 50 g. of ammonium acetate and 60 ml. ofglacial acetic acid was refluxed for two hours. After cooling to roomtemperature, the solution was decanted and the residual tarry solid waswashed with water and isopropanol. The tarry solid was then dissolved in250 ml. of acetone and added dropwise to 1500 ml. of water and 25 g. ofsodium chloride to yield 8.5 g. of4-(4-methoxyphenyl)-2,6-bis[4-(4-morpholinyl)phenyl]pyridine as a paleyellow solid, m.p. 100°-110° C. This product produced a greenish-yellowimage on contact with acidic clay or phenolic resin.

EXAMPLE 28

Following a procedure similar to that described in Example 1 butemploying 4.1 g. of 4-fluorobenzaldehyde, 12.6 g. of4-(1-pyrrolidinyl)acetophenone, 50 g. of ammonium acetate and 60 ml. ofglacial acetic acid there was obtained 2.9 g. of4-(4-fluorophenyl)-2,6-bis[4-(1-pyrrolidinyl)phenyl]pyridine as a lightyellow solid, m.p. 207°-212° C. A chloroform solution of the productdeveloped a reddish orange image when contacted with acidic clay and anorange image when contacted with phenolic resin.

EXAMPLE 29

Following a procedure similar to that described in Example 2 butemploying 3.6 g. of 2-thiophenecarboxaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 35 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 3.6 g. of4-(2-thienyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine as astraw-colored solid, m.p. 191°-198° C. This product produced an orangeimage on contact with acidic clay or phenolic resin.

EXAMPLE 30

Following a procedure similar to that described in Example 11 butemploying 3.3 g. of N-methylpyrrole-2-carboxaldehyde 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 1.5 g. of4-(1-methylpyrrol-2-yl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as agreenish-yellow solid, m.p. 193°-200° C. This product produced a yellowimage on contact with acidic clay or phenolic resin.

EXAMPLE 31

Following a procedure similar to that described in Example 11 butemploying 3.3 g. of 5-methyl-2-furaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 2.2 g. of4-(5-methyl-2-furyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as ayellow solid, m.p. 219.3°-225.5° C. This product produced an orangeimage on contact with acidic clay or phenolic resin.

EXAMPLE 32

Following a procedure similar to that described in Example 11 butemploying 4.4 g. of indole-3-carboxaldehyde, 9.8 g. of4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 4 g. of4-(indol-3-yl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as a yellowsolid, m.p. 237.2°-242.0° C. This product produced a yellowish-orangeimage on contact with acidic clay or phenolic resin.

EXAMPLE 33

Following a procedure similar to that described in Example 1 butemploying 2.3 g. of N-ethyl-3-carbazolecarboxaldehyde, 3.3 g. of4-(dimethylamino)acetophenone, 13.2 g. of ammonium acetate and 15 ml. ofglacial acetic acid there was obtained 2.0 g. of4-(9-ethylcarbazol-3-yl)-2,6-bis[4-(dimethylamino)phenyl]pyridine as ayellow solid, m.p. 157°-173° C. This product produced an orange image oncontact with acidic clay or phenolic resin.

EXAMPLE 34

Following a procedure similar to that described in Example 2 butemploying 3.6 g. of indole-3-carboxaldehyde, 8.1 g. of2-(dimethylamino)acetophenone, 34 g. of ammonium acetate and 30 ml. ofglacial acetic acid there was obtained 3.1 g. of4-(indol-3-yl)-2,6-bis[2-(dimethylamino)phenyl]pyridine, as a paleyellow solid, m.p. 230°-231° C. This product produced a yellow image oncontact with acidic clay or phenolic resin.

EXAMPLE 35

Following a procedure similar to that described in Example 11 butemploying 4.3 g. of indole-3-carboxaldehyde, 21 g. of4-(dibenzylamino)acetophenone, 40 g. of ammonium acetate and 35 ml. ofglacial acetic acid there was obtained 5.4 g. of4-(indol-3-yl)-2,6-bis[4-(dibenzylamino)phenyl]pyridine, as abrownish-yellow solid, m.p. 105.0°-111.8° C. This product produced ayellow image on contact with acidic clay or phenolic resin.

EXAMPLE 36

Following a procedure similar to that described in Example 2 butemploying 3.6 g. of indole-3-carboxaldehyde, 9.5 g. of4-(1-pyrrolidinyl)acetophenone, 36 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 4.1 g. of4-(indol-3-yl)-2,6-bis[4-(1-pyrrolidinyl)phenyl]pyridine, as a tansolid, m.p. 145°-147° C. This product produced a yellow image on contactwith acidic clay or phenolic resin.

EXAMPLE 37

Following a procedure similar to that described in Example 1 butemploying 3.8 g. of 2-thiophenecarboxaldehyde, 13.5 g. of4-(1-pioperidinyl)acetophenone, 50 g. of ammonium acetate and 60 ml. ofglacial acetic acid there was obtained 4.3 g. of4-(2-thienyl)-2,6-bis[4-(1-piperidinyl)phenyl]pyridine, as a lightyellow solid, m.p. 198°-201° C. This product produced an orange colorimage on contact with acidic clay and phenolic resin.

EXAMPLE 38

Following a procedure similar to that described in Example 1 butemploying 4.9 g. of indole-3-carboxaldehyde, 14 g. of4-(4-morpholinyl)acetophenone, 50 g. of ammonium acetate and 60 ml. ofglacial acetic acid there was obtained 7.7 g. of4-(indol-3-yl)-2,6-bis[4-(4-morpholinyl)phenyl]pyridine, as a tan solid,m.p. 270°-275° C. This product produced a greenish yellow image oncontact with acidic clay or phenolic resin.

EXAMPLE 39

Following a procedure similar to that described in Example 2 butemploying 4.8 g. of 2,4-bis(dimethylamino)benzaldehyde, 6.8 g. of4-(dimethylamino)acetophenone, 33 g. of ammonium acetate and 25 ml. ofglacial acetic acid there was obtained 0.3 g. of4-[2,4-bis(dimethylamino)phenyl]-2,6-bis-[4-(dimethylamino)phenyl]pyridine,as a yellow solid, m.p. 235°-260° C. This product produced a yellowishorange image on contact with acidic clay or phenolic resin.

EXAMPLE 40

Following a procedure similar to that described in Example 2 butemploying 11.5 g. of 2-ethoxy-4-(diethylamino)benzaldehyde, 16.3 g. of4-(dimethylamino)acetophenone, 65 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 3.1 g. of4-[2-ethoxy-4-(diethylamino)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a yellow solid, m.p. 100°-110° C. This product produced a yellowishorange image on contact with acidic clay or phenolic resin.

EXAMPLE 41

Following a procedure similar to that described in Example 2 butemploying 5.0 g. of 4-fluorobenzaldehyde, 13.0 g. of4-(dimethylamino)acetophenone, 53 g. of ammonium acetate and 40 ml. ofglacial acetic acid there was obtained 5.1 g. of4-(4-fluorophenyl)-2,6-bis[4-(dimethylamino)phenyl]pyridine, as agreenish-yellow solid, m.p. 185°-187° C. This product produced ayellowish-orange image on contact with acidic clay or phenolic resin.

EXAMPLE 42

Following the procedure similar to that described in Example 11 butemploying 5.5 g. of the ethyl ester of5-(dimethylamino)-2-formyl-benzoic acid, 8.1 g. of4-(dimethylamino)acetophenone, 30 g. of ammonium acetate and 25 ml. ofglacial acetic acid there was obtained 2.7 g. of4-[2-(ethoxycarbonyl)-4-(dimethylamino)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a yellow solid, m.p. 242.5°-252.5° C. This product produced a yellowimage on contact with acidic clay or phenolic resin.

EXAMPLE 43

Following a procedure similar to that described in Example 2 butemploying 4.4 g. of 1-ethyl-2-methylindole-3-carboxaldehyde, 7.7 g. of4-(dimethylamino)acetophenone, 30 g. of ammonium acetate and 25 ml. ofglacial acetic acid there was obtained 2.8 g. of4-(1-ethyl-2-methylindol-3-yl)-2,6-bis[4-(dimethylamino)phenyl]pyridine,as a light yellow solid, m.p. 216°-224° C. This product produced ayellow image on contact with acidic clay or phenolic resin.

EXAMPLE 44

A mixture containing 7.2 g. of 4-(benzylethylamino)benzaldehyde, 10.9 g.of 4-(dimethylamino)acetophenone, 40 g. of ammonium acetate and 25 ml.of glacial acetic acid was heated three hours at 125° C. After coolingto room temperature, the reaction mixture was diluted with water andextracted with toluene. The toluene extracts were washed with waterfollowed by saturated aqueous sodium chloride and evaporated to drynessunder vacuum. The residual oil was crystallized by repeated triturationfirst with hexane and then with isopropyl alcohol. The resulting solidwas collected by filtration, washed with isopropyl alcohol and dried togive 4.2 g. of4-[4-(benzylethylamino)phenyl]-2,6-bis[4-(dimethylamino)phenyl]pyridine,m.p. 157°-163.5° C. This product produced a yellow image on contact withacidic clay or phenolic resin.

It is contemplated that by following procedures similar to thosedescribed in Examples 1, 2, 10, 11, 27 and 44 but employing theappropriately substituted acetophenones and aryl or heteroaryl aldehydesof Formulas II and III, respectively, there will be obtained the 4-aryl-or heteroaryl-2,6-bis[(substituted-amino)phenyl]pyridines of Formula I,Examples 45-47 presented in Table A below:

                                      TABLE A                                     __________________________________________________________________________    Ex.                                                                              Z            R.sub.1                                                                             R.sub.2                                                                             Position of NR.sub.1 R.sub.2                      __________________________________________________________________________    45 C.sub.6 H.sub.5                                                                            (CH.sub.3).sub.2 CH                                                                 (CH.sub.3).sub.2 CH                                                                 4                                                 46 C.sub.6 H.sub.5                                                                            CH.sub.3                                                                            C.sub.2 H.sub.5                                                                     4                                                 47 C.sub.6 H.sub.5                                                                            CH.sub.3                                                                            C.sub.4 H.sub.9                                                                     4                                                 48 5-CH.sub.3 --2-thienyl                                                                     CH.sub.3                                                                            CH.sub.3                                                                            4                                                 49 4-(CH.sub.3).sub.2 CH--C.sub.6 H.sub.4                                                     CH.sub.3                                                                            CH.sub.3                                                                            4                                                 50 2-C.sub.2 H.sub.5 O--3-CH.sub.3 O--C.sub.6 H.sub.3                                         CH.sub.3                                                                            CH.sub.3                                                                            4                                                 51 3-Br--C.sub.6 H.sub.4                                                                      CH.sub.3                                                                            CH.sub.3                                                                            2                                                 52 4-Cl--3-NO.sub.2 --C.sub.6 H.sub.3                                                         C.sub.2 H.sub.5                                                                     C.sub.2 H.sub.5                                                                     4                                                 53 4-t-C.sub.4 H.sub.9 --C.sub.6 H.sub.4                                                      CH.sub.3                                                                            CH.sub.3                                                                            4                                                 54 4-C.sub.4 H.sub.9 O--C.sub.6 H.sub.4                                                       CH.sub.3                                                                            CH.sub.3                                                                            4                                                 55 4-C.sub.4 H.sub.9 O.sub.2 C--C.sub.6 H.sub.4                                               CH.sub.3                                                                            CH.sub.3                                                                            4                                                 56 4-(C.sub.6 H.sub.5 CH.sub.2).sub.2 N--C.sub.6 H.sub.4                                      CH.sub. 3                                                                           CH.sub.3                                                                            2                                                 57 4-(C.sub.4 H.sub.9).sub.2 N--C.sub.6 H.sub.4                                               CH.sub.3                                                                            CH.sub.3                                                                            4                                                 __________________________________________________________________________

EXAMPLE 58

A solution containing 0.73 g. of the color former of Example 3 in 30 g.of isopropylbiphenyl and a solution containing 2.5 g. ofcarboxymethylcellulose in 100 ml. of water were mixed and emulsified byrapid stirring. The desired particle size (5 microns) was checked bymicroscope. To the emulsion was added a solution containing 7.5 g. ofpigskin gelatin in 60 ml. of water. The pH was adjusted to 6.5 with 10%aqueous sodium hydroxide with rapid stirring, and following the gradualaddition of 335 ml. of water at 50° C., the pH was adjusted to 4.5 with10% aqueous acetic acid with continued rapid stirring. After 5 minutesthe mixture was cooled to 15° C., treated with 10 g. of 25% aqueousglutaraldehyde and rapidly stirred for 15 minutes. The resultingmicrocapsule dispersion was stirred more slowly overnight, diluted withwater to 560 g. and coated on white typewriter paper sheets. The sheetswere air-dried. Duplicate typewritten images were made on receivingsheets coated with either phenolic resin or acidic clay. The colorformer of Example 3 produced an orange image on both types of receivingsheets.

EXAMPLE 59

To a solution prepared by dissolving 6.8 g. of terephthaloyl chloride in37.1 g. of hot isopropylbiphenyl and then cooling to 30° C. was added asolution prepared by dissolving 2.1 g. of the color former of Example 1in 34.3 g. of hot isopropylbiphenyl and then cooling to 40° C. Theresulting mixture was slowly added to aqueous polyvinyl alcohol(prepared by diluting 5.9 g. of polyvinyl alcohol having a hydrolysis of87 to 89% with 250 ml. of hot water, cooling to room temperature andfurther diluting with 40 ml. of water) and emulsified under high-shearagitation until a dispersed phase particle size of about 5 microns wasobtained. The resulting emulsion was then stirred at conventional speedwhile adding a solution containing 2.2 g. of sodium carbonate and 3.9 g.of diethylenetriamine in 23 ml. of water. After stirring at roomtemperature for approximately 24 hours, the pH was adjusted to 7.3 with15% aqueous sodium carbonate and the total weight of the suspension wasadjusted to 326 g. by adding water if necessary. The resultingmicrocapsule suspension was then applied to a bond paper sheet (transfersheet) and the coated sheet air-dried. The coated side of the transfersheet was placed in contact with a receiving sheet coated with acidicclay. Writing on the transfer sheet produced an orange duplicate imageon the receiving sheet.

EXAMPLE 60

A polyvinyl alcohol dispersion of the color formers of Examples 2 and 31were prepared by shaking 1 hour on a paint shaker a mixture containing2.0 g. of the color former, 3.7 g. of water, 8.6 g. of 10% aqueouspolyvinyl alcohol and 10 ml. of zirconium grinding beads. Meanwhile apolyvinyl alcohol dispersion of bisphenol A was prepared by shaking amixture containing 9.8 g. of bisphenol A, 18.2 g. of water, 42 g. of 10%aqueous polyvinyl alcohol and 70 ml. of zirconium grinding beads. Thecoating mixture was made by combining and thoroughly mixing 2.1 g. ofthe polyvinyl alcohol dispersion of the color former with 47.9 g. of thepolyvinyl alcohol dispersion of bisphenol A. The coating mixture wasapplied to white mimeo paper sheets and the sheets were dried at roomtemperature. Contacting the coated sheets with a heated stylus at atemperature between 100°-150° C. produced a yellow image on the sheetcoated with the color former of Example 2 and an orange image on thesheet coated with the color former of Example 31.

EXAMPLE 61

A starch paste was prepaed by stirring a mixture containing 15.2 g. oflow-viscosity oxidized starch (sold under the tradename STAYCOM by A. E.Staley Manufacturing Co.) and 60.0 g. of distilled water at roomtemperature until the mixture became homogeneous. The mixture was heatedwith stirring at 90°-93° C. for twenty minutes and then cooled to roomtemperature whereupon the resulting starch paste formed a gel. A starchdispersion of the color former of Example 1 was then prepared by shaking0.5 hr. on a paint shaker a mixture containing 3.3 g. of the starchpaste, 4.0 g. of the color former, 16 g. of distilled water, 17 g. ofglass shot and 4.0 g. of a solution prepared by combining 30 g. ofanhydrous disodium phosphate and 5.6 g. of sodium hydroxide in 100 g. ofdistilled water. Meanwhile a benzoyl peroxide dispersion was prepared byhomogenizing for 0.5 hr. a mixture containing 32.6 g. of the starchpaste, 11.2 g. of low-viscosity oxidized starch, 5.2 g. of benzoylperoxide, 21.6 g. of distilled water, 20 ml. of glass shot and 27 g. ofa solution prepared by combining 5.6 g of sodium hydroxide and 30 g. ofanhydrous disodium phosphate in 100 g. of distilled water. A papercoating mixture was prepared by combining and thoroughly mixing 14.5 g.of the starch dispersion of the color former with 26.2 g. of the starchdispersion of benzoyl peroxide. The resulting mixture was applied towhite mimeo paper sheets and the sheets were dried at room temperature.Contacting the sheets with a heated stylus at a temperature between100°-150° C. produced an orange image.

We claim:
 1. A compound having the formula ##STR10## wherein: R₁ and R₂ are the same or different and are selected from the group consisting of lower-alkyl and benzyl, orNR₁ R₂ is pyrrolidinyl, piperidinyl, or morpholinyl; Z is naphthyl, 9-julolidinyl or a substituent having the formula: ##STR11## wherein R₃, R₄, R₇ and R₈ are hydrogen or non-tertiary lower-alkyl; R₅ is hydrogen, phenyl or non-tertiary lower-alkyl;R₆ is hydrogen, non-tertiary lower-alkyl or non-tertiary lower-alkoxy; X is O or S; Y₁ and Y₂ are the same or different and are selected from the group consisting of hydrogen, lower-alkyl, lower-alkoxy, halo, nitro, lower-alkoxycarbonyl, phenyl or NR₉ R₁₀ ; R₉ is lower-alkyl or benzyl; R₁₀ is lower-alkyl, benzyl, cyano-lower-alkyl, or NR₉ R₁₀ is pyrrolidinyl, piperidinyl, morpholinyl or isoindolinyl.
 2. A compound according to claim 1 wherein Z is naphthyl.
 3. A compound according to claim 2 wherein R₁ and R₂ are each lower-alkyl.
 4. A compound according to claim 1 wherein Z is 9-julolidinyl.
 5. A compound according to claim 4 wherein R₁ and R₂ are each lower-alkyl.
 6. A compound according to claim 1 wherein Z is ##STR12## in which R₃ is hydrogen or non-tertiary lower-alkyl.
 7. A compound according to claim 6 wherein R₁ and R₂ are each lower-alkyl.
 8. A compound according to claim 1 wherein Z is a substituent having the formula ##STR13## wherein R₄ is hydrogen or non-tertiary lower-alkyl;R₅ is hydrogen, phenyl or non-tertiary lower-alkyl, and R₆ is hydrogen, non-tertiary lower-alkyl or non-tertiary lower-alkoxy.
 9. A compound according to claim 8 wherein R₁ and R₂ are the same or different and are selected from the group consisting of lower-alkyl and benzyl.
 10. A compound according to claim 8 wherein NR₁ R₂ is pyrrolidinyl, piperidinyl or morpholinyl.
 11. A compound according to claim 1 wherein Z is ##STR14## in which R₇ is hydrogen or non-tertiary lower-alkyl.
 12. A compound according to claim 11 wherein R₁ and R₂ are each lower-alkyl.
 13. A compound according to claim 1 wherein Z is ##STR15## in which R₈ is hydrogen or non-tertiary lower-alkyl and X is O or S.
 14. A compound according to claim 13 wherein R₁ and R₂ are each lower-alkyl.
 15. A compound according to claim 13 wherein NR₁ R₂ is pyrrolidinyl, piperidinyl or morpholinyl.
 16. A compound according to claim 1 wherein Z is a substituent having the formula ##STR16## wherein Y₁ and Y₂ are the same or different and are selected from the group consisting of hydrogen, lower-alkyl, lower-alkoxy, halo, nitro, lower-alkoxycarbonyl, phenyl or NR₉ R₁₀ ;R₉ is lower-alkyl or benzyl; R₁₀ is lower-alkyl, benzyl or cyano-lower-alkyl, or NR₉ R₁₀ is pyrrolidinyl, piperidinyl, morpholinyl or isoindolinyl.
 17. A compound according to claim 16 wherein at least one of Y₁ and Y₂ is NR₉ R₁₀ in whichR₉ is lower-alkyl or benzyl; R₁₀ is lower-alkyl, benzyl, cyano-lower-alkyl, or NR₉ R₁₀ is pyrrolidinyl, piperidinyl, morpholinyl or isoindolinyl.
 18. A compound according to claim 17 wherein R₁ and R₂ are each lower-alkyl.
 19. A compound according to claim 18 wherein R₉ is lower-alkyl or benzyl and R₁₀ is lower-alkyl, benzyl or cyano-lower-alkyl.
 20. A compound according to claim 19 wherein R₉ and R₁₀ are each lower-alkyl.
 21. 2,4,6-Tris[4-(dimethylamino)phenyl]pyridine according to claim
 20. 22. A compound according to claim 18 wherein NR₉ R₁₀ is pyrrolidinyl, piperidinyl, morpholinyl or isoindolinyl.
 23. A compound according to claim 16 wherein Y₁ and Y₂ are the same or different and are selected from the group consisting of hydrogen, lower-alkyl, lower-alkoxy, halo, nitro, lower-alkoxycarbonyl and phenyl.
 24. A compound according to claim 23 wherein Y₁ and Y₂ are the same or different and are selected from the group consisting of hydrogen, lower-alkyl and lower-alkoxy.
 25. A compound according to claim 24 wherein NR₁ R₂ is pyrrolidinyl, piperidinyl or morpholinyl.
 26. A compound according to claim 24 wherein R₁ and R₂ are each lower-alkyl.
 27. 2,6-bis[4-(Dimethylamino)phenyl]-4-phenylpyridine according to claim
 26. 28. 2,6-bis[4-(Dimethylamino)phenyl]-4-(4-methylphenyl)pyridine according to claim
 26. 29. 2,6-bis[4-(Dimethylamino)phenyl]-4-(4-methoxyphenyl)pyridine according to claim
 26. 